Fig. 2.

CtpA is localized to the bacterial cell wall. (a) A topology model for CtpA localization was generated using memsat (Jones et al., 1994). N-terminal residues 1–38 are located in the bacterial cytosol while a hydrophobic stretch of amino acids from 38 to 61 forms a transmembrane helix. Residues 61–455 are extracellular, located in the cell wall. The catalytic Ser and Lys residues are indicated as filled circles. (b) Western immunoblot analysis of CtpA localization. Histidine-tagged CtpA was expressed from a plasmid in S. aureus. Intracellular, extracellular and bacterial cell-wall protein samples were probed with an anti-histidine antibody.